I E-Mailed Vitesse today about the stage v kit for the 3.0 thinking I can just bolt it on and make 400hp. But I was told that I would have to rebuild the engine with solid internals.

1) I thought that 968 engines came with forged internals and the blocks do not need sleeves.

2) How many psi can I boost with a thicker head gasket?

3) If you had your choice between 951 with a bad turbo or an S2 with a 968 engine, which one would you put your money into. The budget is set at $7000. looking for the best hp for street/track.

 

What kind of track/racing? Drag? Autocross? Road Course?

 

You're limited on making more HP w/ the 968 motor. If you're after big power, stick w/ the 951.

I raced against a friend who transplanted a 968 motor into an S (not S2) and it cost him a lot to have it done. In the end he made slightly less power than my stock turboS.

You can make decent hp without going to a stage V and having to beef up the internals.

 

The 968 engine is capable of making lots of HP. However, the CR must be lowered and heavy duty internals used.
To lower the compression you can:
1 - get custom pistons; expensive but work well
2 - Use a thicker headgasket - there is a thread on a very nice car using this method
3 - Sleeve and get aftermarket pistons

Heavy Duty Internals:
1 - The 968 rods - some are forged. However no one ever tested them to see how much power they can take. You can easily convert to Forged 951 rods.
2 - Depending on which method you use to lower the CR you may not be able to use the 968 pictons.

The bottom line, you cannot bolt a turbo to a 968 as is and make lots of HP. There are some basic items that must be addressed to ensure the success of the project.

 

968 Engine
968 blocks have "filled in" coolant spaces around the bottoms of the cylinders compared to the 951. The coolant jacket goes much lower on the 951. Most of the heat transfer to the block happens at the bottom of the stroke where the 968 block lacks cooling. With the lack of coolant jacket the 968 blocks can get too hot and warp. That is why Porsche added oil squirters and the brace on the bottom of the cylinders. Even with those additions the 968 blocks can still get too hot and warp, especially with the additional heat of forced air induction.

951 vs S2
The only real difference if you are considering replacing the engine is the tranny. The S2 has lower gear ratios targeted for a normally aspirated power curve where the 951 has higher ratios targeted for high rpm boosted power curve.

 

[QUOTE=RKD in OKC;4585737]968 Engine
968 blocks have "filled in" coolant spaces around the bottoms of the cylinders compared to the 951. The coolant jacket goes much lower on the 951. Most of the heat transfer to the block happens at the bottom of the stroke where the 968 block lacks cooling. With the lack of coolant jacket the 968 blocks can get too hot and warp. That is why Porsche added oil squirters and the brace on the bottom of the cylinders. Even with those additions the 968 blocks can still get too hot and warp, especially with the additional heat of forced air induction.QUOTE]

IMHO, you are half correct and half speculating. I think, the bracing is to help keep the 65lb crank from twisting the block like a pretzle. It also braces the bottom of the cylinders and keeps them from moving. The 968 uses way bigger pistons and the block needs help keeping them going up and down vrs sideways, lol.

I might be speculating too but I have line bored checked a bunch of 968 blocks and found them to be pretty straight. I've also line bore check a bunch of 944 blocks and found them to be straight and they are not braced. On the same note, I have found more the a few of each that has the oilpan rails twisted away from each other. These blocks take a beating.

Not to high jack the thread,

If your budget is $7k, I would freshen up the 951 motor and get a turbo from John. A 968 turbo build is much more expensive. There are a lot of extra parts to make and parts to change out to make it last.

 

Autocross & Road Corse.

 

[QUOTE=evil 944t;4585820]yah i think i'm going to stik with the 951.

 

968 rods are not as strong as any of the 944 rods - they are much lighter! The crank is fine for high HP and the block is good as long as it is in good shape. The weak point is the rods and the high compression pistons.

 

Well….not really!
The S2 and 968 blocks don’t have ‘braces’, they are simply covers to keep the oil under control (not getting ‘slung’ up into the cavities)
The block floor is higher on the S2 and 968 blocks because that adds more stability to the cylinders. Almost all the block cooling takes place in the top inch or so of the block – that’s where there is combustion taking place, not at the bottom of the bore. The oil squirters are there to cool the bottom of the piston and lube the wrist pin. This is a carry over from the air cooled engines. Not really needed in the 968 but it is a nice feature for any turbo charged engine – piston temps can really get up there!
S2 / 968 blocks cool just fine. They are much stiffer and in addition have the nice windage port between 1&2 and 3&4.

 

Thanks for that post Chris!



My 2 cents here. Given that budget, stick with a 951 and work it. If you do some reseach on here, there have been few people who have built 3.0Ls. I'm not going to go into it, but you have many options to go about building this. Just take your time and do the research. I would also 'strongly' listen to the advice of people like Chris and John too.

 

I sent you a PM.

 

I suggest S2 or 968 motor.

Autocrosses in the Phoenix area are too narrow to make use of the 951's powerband. Once on track the 951 can use the power, but it will be a dog in most autocrosses.


Of course for 10k or less you can have a nice autocross car and excellent race car. I may not as fast a 951, but when you stuffed in pack of 10 other 944 fighting for position it really does not mater how fast you are going.

 

There goes Joe again, pushing NASA and those 944 spec cars. J/K!

 

Hey.. the guy is local. I can tell you from local experience there are few 951 track cars these days in Phoenix. Quite a few of the "others".

BTW... he can race in one of those 10k cars in SCCA too. They have class as well. Ahh... so does PCA... It not just a NASA thing!